In the case of window films used in buildings and glass, products have been developed by focusing on blocking an ultraviolet range (150 to 380 nm), a visible range (380 to 780 nm) and an infrared range (780 to 23000 nm) depending on the wavelength of the sunlight.
There are various technologies related to the functional film, and for example, there are Patent Documents 1 and 2.
Patent Document 1 relates to a plastic film including a support substrate; and a coating layer formed on at least one surface of the support substrate, in which the coating layer includes a crosslinking copolymer in which 3 to 6 functional acrylate-based monomers and polyrotaxane are copolymerized in a weight ratio of 5:5 to 8:2, and inorganic particles dispersed in the crosslinking copolymer.
Patent Document 2 relates to a display protective film including a base film layer made of polyethylene terephthalate; a first adhesive layer with an acryl-based adhesive formed on one surface of the base film layer; a shock absorbing layer made of thermoplastic polyurethane formed on the first adhesive layer; a second adhesive layer with an acryl-based adhesive formed on the shock absorbing layer; a PET-made surface film layer formed on the second adhesive layer; an anti-glare layer formed on the surface film layer and containing an acrylate-based binder resin and beads having an average particle diameter of 1 to 10 μm on the binder resin; an antimicrobial coating layer formed on the anti-glare layer; a third adhesive layer with a silicone adhesive formed on the other surface of the base film layer; and a release film formed on the third adhesive layer.
As such, various functional films have been developed and used, but in recent years, many color changeable films which are particularly colorful and beautiful in appearance among the window films have been used.
Such a color changeable film is a film which is viewed in different colors depending on a viewing angle and color-changed to various colors such as yellow, red, and blue according to an incident angle of the sunlight.
Such a color changeable film is usually fabricated by laminating 100 to 300 layers of thin PET films, and as the color changeable film is fabricated by laminating the multiple layers, there is a problem that a defective rate increases in the fabricating process. That is, if a foreign substance is inserted between the layers even in any one of the processes of laminating the multiple layers, the defect of the fabric occurs, and thus, there is a problem in that maintenance and management of the manufacturing facility is difficult and the manufacturing cost is increased because a very careful caution is required for the process management.
Meanwhile, a film having pearl is used, but the film having pearl is mainly used for an opaque film.
The reason why the pearl is coated on the opaque film is that there is a problem in that a haze occurs according to the pearl content and a type of synthetic resin ingredient, and when the pearl powder is mixed with a coating agent, the pearl is first evenly dispersed in the coating agent, but over time, the pearl sinks and then the pearl is concentrated only in a portion.
In order to improve the disadvantages, various technologies have been developed and for example, there are Patent Documents 3 and 4.
Patent Document 3 relates to a decoration sheet printed with various patterns in colors including a base layer made of a PET film; a base color printing layer formed by printing a base color on the base layer; a diffused reflection layer formed by coating an acryl adhesive formed by mixing 10 to 20 wt % of a diffused reflection filler and 2 to 10 wt % of a pigment with 70 to 88 wt % of an acrylic adhesive on the base color printing layer; a reinforcing layer formed by bonding the PET film on the diffused reflection layer; a pattern printing layer formed by printing various patterns on the reinforcing layer; a release adhesive layer formed by coating an acrylic adhesive on the pattern printing layer; and a release film layer formed by adhering a release film on the release adhesive layer which are sequentially laminated from the bottom, in which the diffused reflection filler is formed by adding 30 to 40 wt % of a hologram chip, 30 to 40 wt % of pearl, and 30 to 40 wt % of an aluminum chip.
However, the conventional sheet has a disadvantage in that the content of the pearl is too large and the manufacturing cost is high.
Patent Document 4 relates to a method for manufacturing a functional fabric which is constituted by an adhesive resin layer formed on the surface of a fabric, a mica-containing synthetic resin layer formed on the surface of the adhesive resin layer, and a pearl-containing synthetic resin layer formed on the surface of the mica-containing synthetic resin layer, and includes 1 to 50 wt % of pearl particles.
As described above, in the conventional method for manufacturing the functional fabric, there is a disadvantage in that the content of the pearl particles is high, the pearl-containing layer needs to be formed on the synthetic resin, and thus the manufacturing process is complicated and it is unsuitable for using the film as a coating film of automobile glass or the like.
Further, in the case of the conventional film including the pearl, there is a disadvantage in that a haze occurs according to the pearl content and a type of resin ingredient, and when the pearl powder is mixed with the adhesive layer, the pearl is first evenly dispersed, but over time, the pearl particles sink, and thus the film is not used for a transparent window and the like and its use is limited to only an opaque decoration film.